Content supply system and information processing method

ABSTRACT

A center (content supply center) ( 1865 ) for storing and managing contents, and user terminals ( 1861  to  1864 ) used by respective users are connected via networks ( 861  to  867 ). The center ( 1865 ) sends signals of contents for trial viewing/listening to the user terminals for free or at a low price. The user terminals ( 1861  to  1864 ) can receive the signals of the contents for trial viewing/listening and select and purchase only the content that the user likes from the received contents so as to reproduce the content with high quality. This enables trial viewing/listening. It is not necessary to download a large quantity of data with high quality from the content supply center or the like and there will be more opportunities of content purchase.

TECHNICAL FIELD

[0001] This invention relates to a content supply system and aninformation processing method for supplying contents such as audiosignals or image signals, and particularly to a content supply systemand an information processing method in which signals are coded toenable trial viewing/listening and therefore reproduction and recordingwith high quality is made possible by adding a small quantity of datawhen a trial viewer/listener decides to purchase the signals.

BACKGROUND ART

[0002] A content (software) distribution method is known in which, forexample, an acoustic signal or the like is encrypted and then broadcastor recorded to a recording medium so that only a person who purchased akey for decryption is permitted to listen to the signal.

[0003] As an encryption method, for example, a method is known in whichan initial value of a random-number sequence is given as a key signalfor a bit string of a PCM acoustic signal and then a bit string obtainedby taking an exclusive OR between the generated random-number sequenceof 0/1 and the PCM bit string is transmitted or recorded to a recordingmedium. As this method is used, a person who acquired the key signal cancorrectly reproduce the acoustic signal and a person who did not acquirethe key signal can only reproduce noise. Of course, it is also possibleto use a more complicated method such as so-called DES (Data EncryptionStandard) as an encryption method. Description of the DES standard isdisclosed in “Federal Information Processing Standards Publication 46,Specifications for the DATA ENCRYPTION STANDARD, 1977, January 15.”

[0004] On the other hand, a method for compressing an acoustic signaland then broadcasting or recording the compressed acoustic signal to arecording medium is popularized, and recording media which enablerecording of a coded audio signal or the like, such as a magneto-opticaldisc, are broadly used.

[0005] There are various techniques for high-efficiency coding of anaudio signal, voice signal, or the like. For example, such techniquesmay include subband coding (SBC), which is a non-blocked frequency banddivision system for dividing an audio signal or the like on the timeaxis into a plurality of frequency bands without blocking and thencoding the band-divided audio signal, and so-called transform coding,which is a blocked frequency band division system for transforming(spectrally transforming) a signal on the time axis to a signal of thefrequency axis, then dividing the signal into a plurality of frequencybands and coding the signal of each band. Moreover, a high-efficiencycoding technique combining the above-described subband coding withtransform coding is considered. In that case, for example, afterfrequency band division is carried out by the above-described subbandcoding, the signal of each band is spectrally transformed to a signal onthe frequency axis and the spectrally transformed signal of each band iscoded.

[0006] As a filter for the above-described technique, for example, a QMFfilter is used. The QMF filter is described in “R. E. Crochiere, Digitalcoding of speech in subbands, Bell Syst. Tech. J. Vol.55, No.8, 1976.”Moreover, a filter division technique with equal bandwidth is disclosedin “Joseph H. Rothweiler, Polyphase Quadrature Filters—A new subbandcoding technique, ICASSP 83, BOSTON.”

[0007] As the above-described spectral transform, for example, the timeaxis is transformed to the frequency axis by blocking an input audiosignal by predetermined unit time (frame) and then performing discreteFourier transform (DFT), discrete cosine transform (DCT), modifieddiscrete cosine transform (MDCT) or the like on each of the blocks. MDCTis described in “J. P. Princen, A. B. Bradley, Univ. of Surrey RoyalMelbourne Inst. of Tech., Subband/Transform Coding Using Filter BandDesigns Based on Time Domain Aliasing Cancellation, ICASSP, 1987”.

[0008] If the above-described DFT or DCT is used as a method fortransforming a waveform signal to the spectrum, M independentreal-number data are provided by performing transform on a time blockconsisting of M samples. To reduce the connection distortion betweentime blocks, each time block is usually overlapped with both adjacentblocks by M1 samples each. Therefore, on average, M real-number data arequantized and coded for (M-M1) samples in DFT or DCT.

[0009] On the other hand, if the above-described MDCT is used as amethod for transforming a waveform signal to the spectrum, M independentreal-number data are provided from 2M samples as a result of overlappingboth adjacent time blocks by M samples each. Therefore, on average, Mreal-number data are quantized and coded for M samples in MDCT. Adecoding device can reconstruct the waveform signal by performinginverse transform on each block of the code obtained by using MDCT andthen adding the resulting waveform elements while letting them interferewith each other.

[0010] Generally, by elongating a time block for transform, thefrequency resolution of the spectrum is enhanced and the energyconcentrates at a specific spectral component. Therefore, by using MDCTin which each block is overlapped with both adjacent blocks by half eachto perform transform with a longer block length and in which the numberof resulting spectral signals is not increased from the number of theoriginal time samples, more efficient coding can be carried out thanwhen DFT or DCT is used. Moreover, by having each block have asufficient long overlap with the adjacent blocks, the distortion betweenthe blocks of the waveform signal can be reduced.

[0011] By quantizing the signal thus divided to each band by the filteror spectral transform, a band where quantization noise is generated canbe controlled and more auditorily efficient coding can be performed byutilizing characteristics such as masking effect. By carrying outnormalization for each band with the maximum value of absolute values ofsignal components in the band before performing quantization, moreefficient coding can be performed.

[0012] The frequency division width in the case of quantizing eachfrequency component obtained by frequency band division is determined,for example, in consideration of the human auditory characteristic.Specifically, an audio signal may be divided into a plurality of bands(for example 25 bands) with broader bandwidths for higher-frequencybands which are generally called critical bands. When coding data ofeach band in this case, coding is carried out by using predetermined bitdistribution to each band or adaptive bit allocation to each band. Forexample, when coding coefficient/factor data resulting from theabove-described MDCT processing by the above-described bit allocation,the MDCT coefficient/factor data of each band resulting from MDCT ofeach of the blocks is coded by using an adaptive number of allocatedbits.

[0013] For such bit allocation, the following two techniques are known.Specifically, “R. Zelinski and P. Noll, Adaptive Transform Coding ofSpeech Signals, IEEE Transactions of Acoustics, Speech, and SignalProcessing, vol.ASSP-25, No.2, August 1977”, discloses bit allocationbased on the magnitude of a signal of each band. In this system, thoughthe quantization noise spectrum is flat and the noise energy is minimum,the actual perception of noise is not optimum because the auditorymasking effect is not utilized. “M. A. Kransner, MIT, The critical bandcoder—digital encoding of the perceptual requirements of the auditorysystem, ICASSP 1980”, discloses a technique in which a necessarysignal-to-noise ratio for each band is obtained using auditory masking,thus performing fixed bit allocation. With this technique, however, evenwhen measuring characteristics by using a sine wave input, asatisfactory characteristic value is not obtained because of fixed bitallocation.

[0014] To solve these problems, a high-efficiency coding device isproposed in which all the bits that can be used for bit allocation aredivisionally used for a fixed bit allocation pattern predetermined foreach small block and for bit allocation dependent on the magnitude ofthe signal of each block and in which the division ratio depends on asignal related to the input signal so that the proportion of division tothe fixed bit allocation pattern is increased for a smoother spectrum ofthe signal.

[0015] According to this technique, if the energy concentrates at aspecific spectrum, as in a sine wave input, the signal-to-noise ratiocan be significantly improved as a whole by allocating many bits to ablock containing that spectrum. Generally, since the human auditorysense is very sensitive to a signal having an acute spectral component,the improvement in the signal-to-noise ratio by using this technique iseffective not only for improvement in the numerical value in measurementbut also for improvement in the sound quality perceived by the auditorysense.

[0016] Many other techniques for bit allocation are proposed. As theauditory model is elaborated further and the coding device has asufficient capability, more auditorily efficient coding is madepossible. In these techniques, typically, a bit allocation referencevalue of a real number which realizes the signal-to-noise characteristicfound by calculation with high fidelity is found, and an integer whichapproximates the reference value is used as the number of allocatedbits.

[0017] In the specification and drawings of the Japanese PatentApplication No.H5-152865 or WO94/28633 proposed by the presentinventors, a method is proposed in which a tonal component that isparticularly important in terms of the auditory sense, that is, a signalcomponent with energy concentrated around a specific frequency, isseparated from a spectral signal and coded separately from the otherspectral components. This enables efficient coding of an audio signaletc. at a high compression rate while causing little auditorydeterioration.

[0018] To construct an actual code string, first, quantization accuracyinformation and normalization factor (coefficient) information may becoded using a predetermined number of bits for each band on whichnormalization and quantization are performed, and then a normalized andquantized spectral signal may be coded. Moreover, the ISO/IEC11172-3:1993(E), 1993 describes a high-efficiency coding system in whichthe number of bits representing quantization accuracy information is setto vary depending on the band. It is standardized that the number ofbits representing quantization accuracy information is decreased towardhigher frequency bands.

[0019] Instead of directly coding quantization accuracy information, amethod is known in which quantization accuracy information is decidedfrom normalization factor information in a decoding device. In thismethod, however, the relation between normalization factor informationand quantization accuracy information is decided when the standard isset. Therefore, control of the quantization accuracy based on a moreadvanced auditory model cannot be introduced in the future. Moreover, ifthe compression rate to be realized is variable, the relation betweennormalization factor information and quantization accuracy informationmust be defined for each compression rate.

[0020] There is also known a method for more efficient coding by codinga quantized spectral signal using a variable-length code described in“D. A. Huffman, A Method for Construction of Minimum Redundancy Codes,Proc. I.R.E., 40, p.1098 (1952)”.

[0021] Meanwhile, a software distribution method is known in which anacoustic signal or the like coded by the above-described methods isencrypted and broadcast or recorded to a recording medium so that only aperson who purchased a key is permitted to listen to the signal. As anencryption method, for example, a method is known in which an initialvalue of a random-number sequence is given as a key signal for a bitstring of a PCM (pulse code modulation) acoustic signal or a codedsignal and then a bit string obtained by taking an exclusive OR betweenthe generated random-number sequence of 0/1 and the bit string istransmitted or recorded to a recording medium. As this method is used,only a person who acquired the key signal can correctly reproduce theacoustic signal and a person who did not acquire the key signal can onlyreproduce noise. Of course, it is also possible to use a morecomplicated method as an encryption method.

[0022] However, such a method has a problem that a user must firstdecide to purchase a content and then download a large quantity of datawith high quality from a content supply center or the like.

[0023] There is another problem that a user must necessarily access thecontent supply center or the like in order to carry out trialviewing/listening and hence there will be less opportunities of trialviewing/listening.

[0024] Moreover, in the case of music or the like, a user often wants topurchase a tune selected from tunes which the user happens to listen to.However, in the method of accessing the center to select trialviewing/listening, there is a problem that the user will be at a lossabout which tune to select for trial listening.

DISCLOSURE OF THE INVENTION

[0025] In view of the foregoing status of the art, it is an object ofthe present invention to provide a content supply system and aninformation processing method which enable trial viewing/listening,eliminate the need to download a large quantity of data with highquality from a content supply center or the like, and enable increase inthe number of opportunities of content purchase.

[0026] In order to solve the foregoing problems, a content supply systemaccording to the present invention comprises: a content supply centerfor supplying a signal of a first code string in which a part ofinformation of a code string obtained by coding a content is replaced bydummy data and a signal of a second code string for complementing thedummy data part; and a user terminal having a function to arbitrarilyreceive the data of the first code string from the content supplycenter, to receive the signal of the second code string from the contentsupply center in accordance with a predetermined condition, and toreplace the dummy data of the first code string by using the second codestring.

[0027] Thus, it is no longer necessary to download a large quantity ofdata with high quality after deciding to purchase the content.

[0028] Moreover, a content supply system according to the presentinvention comprises a content supply center for sending signals ofcontents for trial viewing/listening to a user terminal for free or at alow price, a user being able to receive the contents for trialviewing/listening from the content supply center and to select andpurchase only the content that the user likes from the received contentsso as to reproduce the content with high quality.

[0029] Thus, since the data for trial viewing/listening is automaticallysent from the center, the user need not access the center for trialviewing/listening and there will be more opportunities of trialviewing/listening.

[0030] Moreover, a content supply system according to the presentinvention permits copying of signals of contents for trialviewing/listening acquired by one user, for free or at a low price, andenables each user who reproduced the copy to select and purchase onlythe content that each user likes from the reproduced copy so as toreproduce the content with high quality.

[0031] Thus, since the trial viewing/listening data is transmittedbetween the users, there will be more opportunities of trialviewing/listening.

[0032] Furthermore, a content supply system according to the presentinvention enables a user to record signals of contents for trialviewing/listening downloaded from a content supply terminal for free orat a low price, reproduce the signals of these contents, and select andpurchase only the content that the user likes from them so as toreproduce the content with high quality.

[0033] Thus, since the trial viewing/listening data is transmittedbetween the users, there will be more opportunities of trialviewing/listening.

[0034] The signals of the contents for trial viewing/listening have anarrow reproducing band. The narrowing of the reproducing band isrealized by embedding dummy data into the code string of the content orby encrypting a part of the code string.

[0035] Moreover, according to the present invention, since a user moreoften purchases a music tune selected from tunes which the user happensto listen to, the user will not be at a loss about which tune to selectfor trial listening and there will be more opportunities of contentpurchase.

[0036] Furthermore, an information processing method according to thepresent invention comprises: a step of generating, from an original codestring obtained by coding original information by a predetermined formatwith a frame structure, a first code string which can be reproduced asinformation having lower quality than the original information butrecognizable by a human being, by replacing a part or a plurality ofparts of the original code string with dummy data; a step of generatinga second code string which enables reproduction of the originalinformation by complementing the first code string, from the part or theplurality of parts of the original code string separated from the firstcode string; a step of supplying the first code string to firstinformation supply means; a step of supplying the second code string tothe first information supply means or second information supply means; astep of distributing the first code string through the first informationsupply means so that at least a part of the first code string is in anaccess-free status; a step of distributing the second code stringthrough the first information supply means or the second informationsupply means so that at least a part of the second code string is in anon-access-free status; a step of reproducing the information havinglower quality than the original information but recognizable by a humanbeing from the first code string, by using information reproducing meanscapable of reproducing the code string coded by the predeterminedformat; and a step of accessing the second code string throughpredetermined processing and reproducing the information from the firstcode string while complementing the first code string with the secondcode string.

[0037] The part or the plurality of parts of the code string to bereplaced by the dummy data may include, for example, a part or all ofcontent information and/or a part or all of control informationnecessary for reproduction of the content information. Moreover, thepart or the plurality of parts of the code string to be replaced can beset to a part or all of frames. Furthermore, the predetermined formatmay be a format for generating a code string, for example, byvariable-length coding the content information and multiplexing it as acode string related to control information necessary for reproduction ofthe content information.

[0038] The access-free status means that an unspecified person cannormally access the code string. That is, the access-free statusincludes not only the status where no access limitation is set on thecode string but also the status where the code string is practicallyaccess-free though an access limitation that can be easily canceled byan unspecified person is set. The non-access-free status means that onlya specified person can normally access the code string.

[0039] The distribution in the non-access-free status can be realized,for example, by performing encryption processing on the code string andthen distributing the code string. In this case, the user cannot accessthe code string unless he/she carries out decryption processing aspredetermined processing.

[0040] Moreover, the distribution in the non-access-free status can berealized, for example, by recording the code string to a copy-protectedstorage medium and physically distributing the storage medium. In thiscase, free access to the code string by the user for a predeterminedperiod may be permitted by utilizing a digital watermarking technique, atime limitation technique and the like.

[0041] In any of the above-described methods for realizing thedistribution in the non-access-free status, it is possible to employsuch a structure that execution of the corresponding predeterminedprocessing by the user is permitted on the assumption of appropriateaccounting, registration of user information, distribution ofadvertising information to the user or confirmation of advertisinginformation by the user, and so on. Alternatively, in any of theabove-described methods for realizing the distribution in thenon-access-free status, it is possible to employ such a structure thatfree execution of the predetermined processing by the user within apredetermined period is permitted but free execution of thepredetermined processing by the user is not permitted after thepredetermined period unless appropriate processing is carried out.

BRIEF DESCRIPTION OF THE DRAWINGS

[0042]FIG. 1 is a block diagram showing a schematic structure of anoptical disc recording/reproducing device used for description of anembodiment of the present invention.

[0043]FIG. 2 is a block diagram showing a schematic structure of anexemplary coding device used for the description of the embodiment ofthe present invention.

[0044]FIG. 3 is a block diagram showing a specific example of transformmeans of the coding device of FIG. 2.

[0045]FIG. 4 is a block diagram showing a specific example of signalcomponent coding means of the coding device of FIG. 2.

[0046]FIG. 5 is a block diagram showing a schematic structure of anexemplary decoding device used for the description of the embodiment ofthe present invention.

[0047]FIG. 6 is a block diagram showing a specific example of inversetransform means of the decoding device of FIG. 5.

[0048]FIG. 7 is a block diagram showing a specific example of signalcomponent decoding means of the decoding device of FIG. 5.

[0049]FIG. 8 is a view for explaining a coding method used for thedescription of the embodiment of the present invention.

[0050]FIG. 9 is a view for explaining a exemplary code string obtainedby the coding method used for the description of the embodiment of thepresent invention.

[0051]FIG. 10 is a view for explaining another exemplary coding methodused for the description of the embodiment of the present invention.

[0052]FIG. 11 is a block diagram showing an example of signal componentcoding means for realizing the coding method explained with reference toFIG. 10.

[0053]FIG. 12 is a block diagram showing an example of signal componentdecoding means used in a decoding device for decoding a code stringobtained by the coding method explained with reference to FIG. 10.

[0054]FIG. 13 is a view showing an exemplary code string obtained by thecoding method explained with reference to FIG. 10.

[0055]FIG. 14 is a view showing an exemplary code string obtained by thecoding method used in the embodiment of the present invention.

[0056]FIG. 15 is a view showing an exemplary spectral signal of areproduced signal when a code string obtained by the coding methodexplained with reference to FIG. 14 is reproduced.

[0057]FIG. 16 is a view showing an exemplary spectral signal of areproduced signal when a code string obtained by another example of thecoding method explained with reference to FIG. 14 is reproduced.

[0058]FIG. 17 is a view showing a schematic structure of a reproducingdevice for realizing the coding method explained with reference to FIG.15.

[0059]FIG. 18 is a view showing an example of information for replacingdummy data of a code string obtained by the coding method explained withreference to FIG. 15.

[0060]FIG. 19 is a block diagram showing a schematic structure of arecording device used in the embodiment of the present invention.

[0061]FIG. 20 is a view showing an example of information for replacingdummy data of a code string obtained by a coding method used in anotherembodiment of the present invention.

[0062]FIG. 21 is a flowchart for explaining a reproducing method used inthe embodiment of the present invention.

[0063]FIG. 22 is a flowchart for explaining a recording method used inthe embodiment of the present invention.

[0064]FIG. 23 is a view showing an exemplary code string obtained byanother coding method used in the embodiment of the present invention.

[0065]FIG. 24 is a view for explaining a change with the lapse of timeof the code string used in the embodiment of the present invention.

[0066]FIG. 25 is a block diagram showing an exemplary coding device usedin the embodiment of the present invention.

[0067]FIG. 26 is a flowchart for explaining the coding method used inthe embodiment of the present invention.

[0068]FIG. 27 is a view for explaining the processing to extract only ahigh-quality part in the case where the reproduction quality of the codestring changes with the lapse of time.

[0069]FIGS. 28A and 28B are views for explaining other coding methodsused in the embodiment of the present invention.

[0070]FIG. 29 is a block diagram for explaining a content supply systemconstituted by using the embodiment of the present invention.

[0071]FIG. 30 is a block diagram showing an exemplary user terminal usedin the content supply system of FIG. 29.

[0072]FIG. 31 is a block diagram showing an example of control means ofthe user terminal of FIG. 30.

[0073]FIG. 32 is a block diagram for explaining a content supply systemconstituted by using another embodiment of the present invention.

[0074]FIG. 33 is a block diagram for explaining a content supply systemconstituted by using still another embodiment of the present invention.

[0075]FIG. 34 is a block diagram for explaining a reproducing terminalused in the content supply system of FIG. 33.

BEST MODE FOR CARRYING OUT THE INVENTION

[0076] Prior to the description of embodiments of the present invention,an optical recording/reproducing device as a typical compressed datarecording/reproducing device used for the description of the embodimentsof the present invention will be first described with reference to thedrawings.

[0077]FIG. 1 is a block diagram showing an exemplary optical discrecording/reproducing device. In the device shown in FIG. 1, first, amagneto-optical disc 1 rotationally driven by a spindle motor 51 is usedas a recording medium. When recording data to the magneto-optical disc1, for example, a modulation magnetic field corresponding to the data tobe recorded is applied by a magnetic head 54 while a laser beam is castby the optical head 53, thus performing so-called magnetic fieldmodulation recording so as to record the data along recording tracks ofthe magneto-optical disc 1. When reproducing data, the recording tracksof the magneto-optical disc 1 are traced by a laser beam from themagnetic head 53, thus performing magneto-optical reproduction.

[0078] The optical head 53 is constituted by, for example, a laser lightsource such as a laser diode, optical components such as a collimatinglens, an objective lens, a polarizing beam splitter and a cylindricallens, and a photodetector having a light receiving part of apredetermined pattern. This optical head 53 is provided at a positionopposite to the magnetic head 54 with the magneto-optical disc 1provided between them. When recording data to the magneto-optical disc1, the magnetic head 54 is driven by a head driving circuit 66 of arecording system, which will be described later, to apply a modulationmagnetic field corresponding to the data to be recorded, and a laserbeam is cast onto a target track of the magneto-optical disc 1 by theoptical head 53, thereby performing thermomagnetic recording based on amagnetic field modulation system. The optical head 53 detects areflected beam of the laser beam cast onto the target track, thusdetecting a focusing error by a so-called astigmatic method, forexample, and also detecting a tracking error by a so-called push-pullmethod, for example. When reproducing data from the magneto-optical disc1, the optical head 53 detects the focusing error and the tracking errorand detects, at the same time, the difference in the polarization angle(Kerr rotation angle) of the reflected beam of the laser beam from thetarget track, thus generating a reproduced signal.

[0079] The output of the optical head 53 is supplied to an RF circuit55. The RF circuit 55 extracts the focusing error signal and thetracking error signal from the output of the optical head 53 andsupplies these signals to a servo control circuit 56. The RF circuit 55also binarizes the reproduced signal and supplies the binary signal to adecoder 71 of a reproducing system, which will be described later.

[0080] The servo control circuit 56 is constituted by, for example, afocusing servo control circuit, a tracking servo control circuit, aspindle motor servo control circuit, a thread servo control circuit andthe like. The focusing servo control circuit performs focusing controlof the optical system of the optical head 53 so that the focusing errorsignal becomes zero. The tracking servo control circuit performingtracking control of the optical system of the optical head 53 so thatthe tracking error signal becomes zero. The spindle motor servo controlcircuit controls the spindle motor 51 to rotationally drive themagneto-optical disc 1 at a predetermined rotation speed (for example,constant linear velocity). The thread servo control circuit moves theoptical head 53 and the magnetic head 54 to the position of the targettrack on the magneto-optical disc 1 designated by a system controller57. The servo control circuit 56, which carries out such various controloperations, sends the system controller 57 information indicating theoperating status of each part controlled by the servo control circuit56.

[0081] The system controller 57 is connected with a key input operatingunit 58 and a display unit 59. The system controller 57 controls therecording system and the reproducing system in accordance with operationinput information from the key input operating unit 58. The systemcontroller 57 also manages the recording position and the reproducingposition on a recording track which is being traced by the optical head53 and the magnetic head 54, on the basis of address information of eachsector reproduced from the recording track of the magneto-optical disc 1by using header time and subcode Q-data. Moreover, the system controller57 controls the display unit 59 to display the reproducing time on thebasis of the data compression rate of the compressed datarecording/reproducing device and the reproducing position information onthe recording track.

[0082] For the display of the reproducing time, address information(absolute time information) of each sector reproduced from the recordingtrack of the magneto-optical disc 1 by using header time and so-calledsubcode Q-data is multiplied by the reciprocal of the data compressionrate (for example, 4 in the case of ¼ compression), thus finding theactual time information. The time information thus found is displayed onthe display unit 59. Also in recording, if absolute time information hasbeen recorded in advance (pre-formatted) on a recording track of, forexample, a magneto-optical disc or the like, the pre-formatted absolutetime information can be read and multiplied by the reciprocal of thedata compression rate, thus displaying the current position as theactual recording time.

[0083] In the recording system of the optical disc recording/reproducingdevice shown in FIG. 1, an analog audio input signal A_(IN) from aninput terminal 60 is supplied to an A/D converter 62 via a low-passfilter 61. The A/D converter 62 quantizes the analog audio input signalA_(IN). A digital audio signal thus obtained by the A/D converter 62 issupplied to an ATC (adaptive transform coding) encoder 63. Moreover, adigital audio input signal D_(IN) from an input terminal 67 is suppliedto the ATC encoder 63 via a digital input interface 68. The ATC encoder63 performs bit compression (data compression) processing in accordancewith a predetermined data compression rate with respect to digital audioPCM data of a predetermined transfer rate resulting from thequantization of the input signal A_(IN) by the A/D converter 62. Thecompressed data (ATC data) outputted from the ATC encoder 63 is suppliedto a memory (RAM) 64. For example, if the data compression rate is ⅛,the data transfer rate is lowered to ⅛ (9.375 sectors/second) of thedata transfer rate (75 sectors/second) of a so-called CD-DA format,which is a standard digital audio CD format.

[0084] Writing and reading of data to and from the memory (RAM) 64 arecontrolled by the system controller 57. The memory 64 is used as abuffer memory for temporarily storing the ATC data supplied from the ATCencoder 63 and recording the ATC data onto a disc, when necessary. Thatis, for example, if the data compression rate is ⅛, the data transferrate of the compressed audio data supplied from the ATC encoder 63 islowered to ⅛ of the data transfer rate (75 sectors/second) of thestandard CD-DA format, that is, 9.375 sectors/second. This compresseddata is continuously written to the memory 64. For the compressed data(ATC data), recording of every eighth sector is enough as describedabove. However, since such recording of every eighth sector ispractically almost impossible, the following sector-continuous recordingis carried out.

[0085] This recording is carried out in a burst-like manner with aquiescent time at the same data transfer rate (75 sectors/second) as thestandard CD-DA format, using a cluster made up of a predeterminedplurality of sectors (for example, 32 sectors plus several sectors) as arecording unit. Specifically, from the memory 64, the ATC data havingthe data compression rate of ⅛, which is continuously written at the lowtransfer rate of 9.375 (=75/8) sectors/second corresponding to the bitcompression rate, is read out as recording data in a burst-like mannerat the transfer rate of 75 sectors/second. For this data, which is readout and then recorded, the data transfer rate as a whole including therecording quiescent time is the above-described low data transfer rateof 9.375 sectors/second, but the instantaneous data transfer rate withinthe time of the burst-like recording is the standard data transfer rateof 75 sectors/second. Therefore, when the disc rotation speed is thesame as the standard CD-DA format (constant linear velocity), recordingwith the same recording density and recording pattern as the CD-DAformat is carried out.

[0086] The ATC audio data, that is, the recording data read out from thememory 64 in a burst-like manner at the (instantaneous) transfer rate of75 sectors/second is supplied to an encoder 65. In the data stringsupplied from the memory 64 to the encoder 65, a unit of recordingcontinuously recorded in one recording consists of a cluster made up ofa plurality of sectors (for example, 32 sectors) and several sectors forcluster connection arranged before and after the cluster. The sectorsfor cluster connection are set to be longer than the interleave lengthin the encoder 65 so that interleave will not affect data of the otherclusters.

[0087] The encoder 65 performs encoding processing (parity addition andinterleave processing) or EFM coding processing for error correctionwith respect to the recording data supplied from the memory 64 in aburst-like manner as described above. The recording data on which thecoding processing was performed by the encoder 65 is supplied to themagnetic head driving circuit 66. The magnetic head driving circuit 66is connected with the magnetic head 54 and drives the magnetic head 54to apply a modulation magnetic field corresponding to the recording datato the magneto-optical disc 1.

[0088] The system controller 57 performs memory control of the memory 64as described above and also controls the recording position so as tocontinuously record the recording data read out from the memory 64 in aburst-like manner in accordance with this memory control, to therecording track of the magneto-optical disc 1. The recording position iscontrolled as the system controller 57 manages the recording position ofthe recording data read out from the memory 64 in a burst-like mannerand sends a control signal designating a recording position on therecording track of the magneto-optical disc 1 to the servo controlcircuit 56.

[0089] The reproducing system of the optical disc recording/reproducingdevice shown in FIG. 1 will now be described. This reproducing system isadapted for reproducing recording data continuously recorded on therecording track of the magneto-optical disc 1 by the above-describedrecording system. The reproducing system has a decoder 71 to which areproduced output obtained by tracing the recording track of themagneto-optical disc 1 with a laser beam by the optical head 53 andbinarized by the RF circuit 55 is supplied. In this case, data can beread not only from a magneto-optical disc but also from areproduction-only disc which is the same as a so-called CD (compactdisc) and an optical disc of a so-called CD-R type.

[0090] The decoder 71 corresponds to the encoder 65 in theabove-described recording system. The decoder 71 performs processingsuch as decoding processing or EFM decoding processing for errorcorrection as described above with respect to the reproduced outputbinarized by the RF circuit 55, and reproduces the ATC audio data havingthe above-described compression rate of ⅛ at a transfer rate of 75sectors/second, which is higher than the normal transfer rate. Thereproduced data obtained by this decoder 71 is supplied to a memory(RAM) 72.

[0091] Writing and reading of data to and from the memory (RAM) 72 arecontrolled by the system controller 57. The reproduced data suppliedfrom the decoder 71 at the transfer rate of 75 sectors/second is writtento the memory 72 in a burst-like manner at the same transfer rate of 75sectors/second. From the memory 72, the reproduced data written in aburst-like manner at the transfer rate of 75 sectors/second iscontinuously read out at a transfer rate of 9.375 sectors/second, whichcorresponds to the data compression rate of ⅛.

[0092] The system controller 57 performs memory control to write thereproduced data to the memory 72 at the transfer rate of 75sectors/second and to continuously read out the reproduced data from thememory 72 at the transfer rate of 9.375 sectors/second. The systemcontroller 57 performs memory control of the memory 72 as describedabove and also controls the reproducing position so as to continuouslyreproduce the reproduced data written from the memory 72 in a burst-likemanner in accordance with this memory control, from the recording trackof the magneto-optical disc 1. The recording position is controlled asthe system controller 57 manages the reproducing position of thereproduced data read out from the memory 72 in a burst-like manner andsends a control signal designating a reproducing position on therecording track of the magneto-optical disc 1 or the optical disc 1 tothe servo control circuit 56.

[0093] The ATC audio data obtained as the reproduced data continuouslyread out from the memory 72 at the transfer rate of 9.375 sectors/secondis supplied to an ATC decoder 73. The ATC decoder 73 corresponds to theATC encoder 63 of the recording system. The ATC decoder 73 reproduces16-bit digital audio data, for example, by performing data expansion(bit expansion) of the ATC data to eight times. The digital audio datafrom the ATC decoder 73 is supplied to a D/A converter 74.

[0094] The D/A converter 74 converts the digital audio data suppliedfrom the ATC decoder 73 to an analog signal and thus forms an analogaudio output signal A_(OUT). The analog audio signal A_(OUT) obtained bythe D/A converter 74 is outputted from an output terminal 76 via alow-pass filter 75.

[0095] The high-efficiency coding of a signal will now be described indetail. Specifically, the technique of high-efficiency coding an inputdigital signal such as an audio PCM signal by using subband coding(SBC), adaptive transform coding (ATC) and adaptive bit allocation willbe described with reference to FIG. 2 and the subsequent drawings.

[0096]FIG. 2 is a block diagram showing a specific example of anacoustic waveform signal coding device used for the description of theembodiment of the present invention. In this example, an inputted signalwaveform signal 101 is transformed to signals 102 of respective signalfrequency components by transform means 1101. After that, each componentis coded by signal component coding means 1102 and a code string 104 isgenerated by code string generation means 1103.

[0097]FIG. 3 shows a specific example of the transform means 1101 ofFIG. 2. A signal divided into two bands by a band division filter istransformed to spectral signal components 221, 222 of the respectivebands by forward spectral transform means 1211, 1212 using MDCT or thelike. A signal 201 of FIG. 3 corresponds to the signal 101 of FIG. 2 andthe signals 221, 222 of FIG. 3 correspond to the signals 102 of FIG. 2.At the transform means shown in FIG. 3, the bandwidth of the signal ofthe signals 221, 222 is half the bandwidth of the signal 201 and each ofthe signals 221, 222 is decimated to a half of the signal 201. As thetransform means, various other transform means than this specificexample may be considered. For example, the input signal may be directlytransformed to a spectral signal by MDCT. Alternatively, the inputsignal may be transformed by DFT (discrete Fourier transform) or DCT(discrete cosine transform) instead of MDCT. While the signal can bedivided into band components by a so-called band division filter, it isconvenient to employ a method of transforming the signal to frequencycomponents by the above-described spectral transform in which manyfrequency components can be obtained by a relatively small quantity ofarithmetic operation.

[0098]FIG. 4 shows a specific example of the signal component codingmeans 1102 of FIG. 2. An input signal 301 is normalized for eachpredetermined band (to generate a signal 302) by normalization means1301. After that, the signal is quantized by quantization means 1303 onthe basis of quantization accuracy information 303 calculated byquantization accuracy decision means 1302, and a signal 304 is takenout. The signal 301 of FIG. 4 corresponds to the signal 102 of FIG. 2and the signal 304 corresponds to the signal 103 of FIG. 2. However, thesignal 304 contains normalization factor information and quantizationaccuracy information as well as the quantized signal components.

[0099]FIG. 5 is a block diagram showing a specific example of a decodingdevice for outputting an acoustic signal from a code string generated bythe coding device shown in FIG. 2. In this specific example, codes 402of respective signal components are extracted from a code string 401 bycode string resolution means 1401. After respective signal components403 are restored from the codes 402 by signal component decoding means1402, an acoustic waveform signal 404 is outputted by inverse transformmeans 1403.

[0100]FIG. 6 shows a specific example of the inverse transform means1403 of FIG. 5, which corresponds to the specific example of thetransform means of FIG. 3. Signals 511, 512 of respective bands obtainedby inverse spectral transform means 1501, 1502 are synthesized by a bandsynthesis filter 1511. The signals 501, 502 of FIG. 6 correspond to thesignals 403 of FIG. 5 and a signal 521 of FIG. 6 corresponds to thesignal 404 of FIG. 5.

[0101]FIG. 7 shows a specific example of the signal component decodingmeans 1402 of FIG. 5. A signal 551 of FIG. 7 corresponds to the signal402 of FIG. 5 and a signal 553 of FIG. 7 corresponds to the signal 403of FIG. 5. The spectral signal 551 is de-quantized (to a signal 525) byinversal-quantization means 1551 and then de-normalized byinversal-normalization means 1552, and the signal 553 is taken out.

[0102]FIG. 8 is a view for explaining a conventional coding method inthe coding device shown in FIG. 2. In this example shown in FIG. 8, aspectral signal is obtained by the transform means of FIG. 3. FIG. 8shows the absolute value of the spectrum of MDCT with its levelconverted to dB. An input signal is transformed to, for example, 64spectral signals for each predetermined time block, and normalizationand quantization of these spectral signals are carried out for eightbands b1 to b8 each (hereinafter referred to as coding unit). By varyingthe quantization accuracy for each coding unit depending on thedistribution of frequency components, highly auditorily efficient codingis possible in which deterioration in the sound quality is restrained tothe minimum.

[0103]FIG. 9 shows a specific example in the case where a signal codedas described above is recorded to a recording medium. In this specificexample, a fixed-length header containing a synchronizing signal SC isattached to the leading end of each frame, and the number of codingunits UN is recorded in this header. The header is followed byquantization accuracy information QN, which is recorded by the number ofcoding units. After that, normalization factor information NP isrecorded by the number of coding units. Normalized and quantizedspectral coefficient information SP is subsequently recorded. In thecase of a fixed-length frame, a vacant area may be provided after thespectral coefficient information SP. In the example of FIG. 9, thespectral signal of FIG. 8 is coded. As the quantization accuracyinformation QN, for example, 6 bits of a coding unit of the lowestfrequency band to 2 bits of a coding unit of the highest frequency bandare allocated as shown in FIG. 9. As the normalization factorinformation NP, for example, values of 46 of the coding unit of thelowest frequency band to 22 of the coding unit of the highest frequencyband are allocated as shown in FIG. 9. As this normalization factorinformation NP, values proportional to, for example, dB values, areused.

[0104] It is possible to further improve the coding efficiency in theabove-described method. For example, by allocating a relatively shortcode length to a spectral signal with a high frequency, of the quantizedspectral signals, and a relatively long code length to a spectral signalwith a low frequency, the coding efficiency can be improved. Moreover,the quantity of sub information such as quantization accuracyinformation and normalization factor information can be relativelyreduced and the frequency resolution can be improved by providing a longtransform block length. Therefore, as the quantization accuracy can bemore minutely controlled on the frequency axis, the coding efficiencycan be improved.

[0105] Furthermore, the specification and drawings of the JapanesePatent Application No.H5-152865 or WO94/288633 by the present inventorsproposes a method of separating an auditorily important tonal component,that is, a signal component having energy concentrated around a specificfrequency, from a spectral signal, and separately coding the signalcomponent from the other spectral components. This enables efficientcoding at a high compression rate with little deterioration in theauditory sound quality of audio signals.

[0106]FIG. 10 is a view for explaining the case where coding is carriedout by using such a method. FIG. 10 shows the separation and coding oftonal components having particularly high levels, for example, as tonalcomponents Tn1 to Tn3, from a spectral signal. While positioninformation, for example, position data Pos1 to Pos3 are required forthe tonal components Tn1 to Tn3, the spectral signal from which thetonal components Tn1 to Tn3 were extracted can be quantized with a smallnumber of bits. Therefore, by applying this method to a signal havingenergy concentrated at a specific frequency, particularly efficientcoding is made possible.

[0107]FIG. 11 shows the structure of the signal component coding means1102 of FIG. 2 in the case where a tonal component is thus separated andcoded. The output signal 102 (signal 601 of FIG. 11) from the transformmeans 1101 of FIG. 2 is separated into a tonal component (signal 602)and a non-tonal component (signal 603) by tonal component separationmeans 1601, then coded by tonal component coding means 1602 andnon-tonal component coding means 1603, respectively, and taken out assignals 604 and 605, respectively. The tonal component coding means 1602and the non-tonal component coding means 1603 have a structure similarthe structure shown in FIG. 4, but the tonal component coding means 1602also performs coding of the position information of the tonal component.

[0108] Similarly, FIG. 12 shows the structure of the signal componentdecoding means 1402 of FIG. 5 in the case where a tonal component isseparated and coded as described above. A signal 701 of FIG. 12corresponds to the signal 604 of FIG. 11 and a signal 702 of FIG. 12corresponds to the signal 605 of FIG. 11. The signal 701 is decoded bytonal component decoding means 1701 and sent as a signal 703 to spectralsignal synthesis means 1703. The signal 702 is decoded by non-tonalcomponent decoding means 1702 and sent to the spectral signal synthesismeans 1703. The spectral signal synthesis means 1703 synthesizes thetonal component (signal 703) and the non-tonal component (signal 704)and outputs a signal 705.

[0109]FIG. 13 shows a specific example in the case where a signal codedas described above is recorded to a recording medium. In this specificexample, a tonal component is separated and coded, and its code stringis recorded in a part between a header part and quantization accuracyinformation QN. In the tonal component string, the number of tonalcomponents information TN is first recorded and data of each tonalcomponents are recorded then. The data of the tonal components includeposition information P, quantization accuracy information QN,normalization factor information NP and spectral coefficient informationSP. Moreover, in this specific example, a transform block length fortransform to a spectral signal is made twice that of the specificexample of FIG. 9, thus improving the frequency resolution. Furthermore,by introducing a variable-length code, a code string of an acousticsignal corresponding to a length twice that of the specific example ofFIG. 9 is recorded in a frame having the same number of bytes.

[0110] In the above description, the technique preceding the descriptionof the embodiment of the present invention is explained. In theembodiment of the present invention, for example, in the case ofapplying this technique to audio, the content of an audio signal ofrelatively low quality is made free to listen to for trial listening,and an audio signal of high quality is made available for listening bypurchasing or otherwise acquiring additional data of a relatively smallquantity.

[0111] Specifically, in the embodiment of the present invention, forexample, in a part to be coded as shown in FIG. 9, data indicating O-bitallocation is coded in four coding units on the high-frequency side asdummy quantization accuracy data within quantization accuracyinformation QN, and normalization factor information 0 of the minimumvalue is coded in four coding units on the high-frequency side as dummynormalization factor data within normalization factor information NP, asshown in FIG. 14. (In this specific example, the normalization factorhas a value proportional to the dB value.) By thus setting 0 as thequantization accuracy information on the high-frequency side, spectralcoefficient information in a Neg area shown in FIG. 14 is actuallyneglected. As this is reproduced by an ordinary reproducing device,narrow-band data having a spectrum as shown in FIG. 15 will bereproduced. Moreover, by coding the dummy data for the normalizationfactor information, it becomes more difficult to conjecture thequantization accuracy information and carry out unauthorizedreproduction of high-quality data.

[0112] In a signal reproducing device and method used for the embodimentof the present invention, when reproducing a code string of apredetermined format obtained by coding a signal, dummy data of a firstcode string in which a part of the code string of the predeterminedformat is the dummy data is rewritten by using a second code string forcomplementing the dummy data part, and the first code string and thecode string obtained by the rewriting are switched and outputted inaccordance with a predetermined condition.

[0113] In a signal recording device and method used for the embodimentof the present invention, when recording a code string of apredetermined format obtained by coding a signal, dummy data of a firstcode string in which at least a part of the code string of thepredetermined format is the dummy data is rewritten by using a secondcode string for complementing the dummy data part.

[0114] The quantization accuracy information and the normalizationfactor information of all the bands may be replaced by dummy data. Inthis case, no significant data can be reproduced by an ordinaryreproducing device. In order to carry out trial viewing/listening, apart of the dummy data is rewritten and reproduced by using a partialcode string of the second code string (for example, data on thelow-frequency side of the quantization accuracy information and thenormalization factor information). If reproduction of a high-qualitysignal is desired, the quantization accuracy information and thenormalization factor information corresponding to the remaining dummydata, that is, a code string of the part other than the foregoingpartial code string in the second code string, may be purchased orotherwise acquired as additional data to complement all the dummy data.This enables reproduction of a high-quality signal (high sound qualityor high image quality). By changing the quantity of the partial codestring of the second code string, the quality of a signal for trialviewing/listening can be arbitrarily changed.

[0115] In the above-described example, both the quantization accuracyinformation and the normalization factor information are replaced bydummy data. However, it is also conceivable to replace only one of themwith dummy data. If only the quantization accuracy information isreplaced by dummy data of O-bit data, narrow-band data having a spectrumas shown in FIG. 15 is reproduced. On the other hand, if only thenormalization factor information is replaced by dummy data having avalue of 0, a spectrum as shown in FIG. 16 is provided. Although thespectrum on the high-frequency side is not strictly 0, it is practically0 in view of the audibility. In the embodiment of the present invention,the signal of this case, too, is referred to as narrow-band signal.

[0116] Depending on which of the quantization accuracy information andthe normalization factor information is to be replaced by dummy data,the possibility that their true values might be conjectured to performhigh-quality reproduction is different. The case where both thequantization accuracy information and the normalization factorinformation are replaced by dummy data is the most secure case becausethere is no data for conjecturing their true values. In the case whereonly the quantization accuracy information is replaced by dummy data,for example, if the original bit allocation algorithm is adapted forfinding the quantization accuracy information on the basis of thenormalization factor, there is a relatively high possibility that thequantization accuracy information might be conjectured on the basis ofthe normalization factor information. On the other hand, since it isrelatively difficult to find the normalization factor information fromthe quantization accuracy information, the method of replacing only thenormalization factor information with dummy data has a lower possibilitythan the method of replacing only the quantization accuracy informationwith dummy data. Depending on the band, the quantization accuracyinformation or the normalization factor information may be selectivelyreplaced by dummy data.

[0117] Moreover, a part of the spectral coefficient information may bereplaced by dummy data. Particularly since a spectrum in theintermediate-frequency band is significant in terms of the soundquality, data of this part may be replaced by dummy data of 0 and dataof the intermediate/high-frequency band may be replaced by dummyquantization accuracy information or dummy normalization factorinformation. The dummy data need not necessarily be 0. For example, invariable-length coding, an arbitrary code which is shorter than a codeexpressing the true numerical value may be used for replacement. In thatcase, the band where the data is replaced by dummy quantization accuracyinformation or dummy normalization factor information covers the bandwhere a part of the spectral coefficient information is replaced bydummy data, thus performing correct narrow-band reproduction.Particularly, in the case where a variable-length code is used forcoding the spectral coefficient information, if a part of theinformation of the intermediate-frequency band is missing, data ofhigher-frequency bands cannot be decrypted.

[0118] In any case, conjecture of relatively large data including thecontent of a signal is more difficult than decryption of a relativelyshort key length used for ordinary encryption, and for example, thepossibility of infringement on the copyright of a right holder of a tuneis lowered. Moreover, even if dummy data is conjectured with respect toa certain tune, there is no possibility of expansion of damage to othertunes, unlike the case where a decryption method for the encryptionalgorithm is made known. Also in this respect, higher security isprovided than in the case where particular encryption is performed.

[0119]FIG. 17 is a block diagram showing an exemplary reproducing deviceused for the embodiment of the present invention, which is animprovement of the conventional decoding means shown in FIG. 5.

[0120] In FIG. 17, an input signal 801 is a code string (first codestring) a part of which is replaced by dummy data. In this case, thequantization accuracy information and the normalization factorinformation of all the bands or on the high-frequency side are replacedby dummy data. The signal 801, which is a high-efficiency coding signalhaving the dummy data embedded therein, is received, for example, via apredetermined public network (ISDN (Integrated Services DigitalNetwork), satellite network, analog network or the like) and inputted tocode string resolution means 1801. First, the content of the code stringof the signal is resolved by the code string resolution means 1801 andsent as a signal 802 to code string rewriting means 1802 and a selectedterminal b of a switch 1808. The code string rewriting means 1802receives true quantization accuracy information and normalization factorinformation 806 of a second code string for complementing the dummy datapart as a signal 807 through control means 1805. The code stringrewriting means 1802 rewrites the dummy part of the quantizationaccuracy information and the normalization factor information by usingthe signal 807 and sends the result of rewriting to a selected terminala of the switch 1808. The output from the switch 1808 is sent to signalcomponent decoding means 1803. The signal component decoding means 1803decodes the data to spectral data 804 and inverse transform means 1804transforms the spectral data 804 to time series data 805, thusreproducing the audio signal.

[0121] In the structure shown in FIG. 17, in the case of the trialviewing/listening mode, the signal 802 from the code string resolutionmeans 1801 bypasses the code string rewriting means 1802 and is inputtedto the signal component decoding means 1803 via the selected terminal bof the switch 1808. In the case of the purchase mode, the truequantization accuracy information and/or true normalization factorinformation 806 for replacing the above-described dummy data is inputtedto the control means 1805 via the same public network as the signal 801.The control means 1805 rewrites the dummy data in the high-efficiencycoding signal 801 having the dummy data embedded therein which isinputted to the code string rewriting means 1802, by using the truequantization accuracy information and/or true normalization factorinformation 806. A high-efficiency coding signal 803 obtained as aresult of this rewriting is inputted to the signal component decodingmeans 1803 via the selected terminal a of the switch 1808.

[0122] Thus, the user can listen to trial listening music of low soundquality to which the dummy data is added, in the trial viewing/listeningmode, and can listen to music of high sound quality when a predeterminedpurchase procedure (accounting, authentication and the like) is done.

[0123] In the above-described specific example, all the dummy data isrewritten (complemented) using the second code string. However, thepresent invention is not limited to this example and it is also possibleto rewrite at least a part of the dummy data by using a partial codestring of the second code string and then reproduce the data. In thecase of thus replacing at least a part of the dummy data by using thepartial code string of the second code string and then reproducing thedata, for example, the quality (sound quality or image quality) of thetrial viewing/listening can be arbitrarily changed by arbitrarilychanging the proportion of the partial code string of the second codestring. In this case, even in the trial viewing/listening mode, thepartial code string of the second code string is inputted as the signal806 to the control means 1805 and then sent as the signal 807 to thecode string rewriting means 1802. Therefore, a part of the dummy dataembedded in the first code string from the code string resolution means1801 may be rewritten by using the partial code string of the secondcode string and the switch 1808 may be switched to connect to theselected terminal a, thus sending the result of rewriting to the signalcomponent decoding means 1803.

[0124] When the coding system is a system for spectrally transforming acontent signal, dividing its band and generating a code string of apredetermined format containing quantization accuracy information,normalization factor information and spectral coefficient informationfor each band, the dummy data corresponds to at least a part of at leastone of the quantization accuracy information, the normalization factorinformation and the spectral coefficient information. In this case, thepartial code string of the second code string is information on thelow-frequency side of the dummy data. Specifically, for example, whenthe dummy data is of information on the high-frequency side of thequantization accuracy information or information on the high-frequencyside of the normalization factor information, the partial code string ofthe second code string is information on the low-frequency side of thequantization accuracy information or the normalization factorinformation corresponding to the dummy data.

[0125] When the dummy data rewriting data (partial code string of thesecond code string) is for all the bands or approximately all the bandsof the information corresponding to the dummy data, an audio signalhaving a broad band and high quality is reproduced. When the dummy datarewriting data (partial code string of the second code string) is for apartial narrow band of the information corresponding to the dummy data,an audio signal having a narrow band is reproduced. Thus, depending onthe bandwidth to which the dummy data rewriting data corresponds, thesound quality of trial listening can be controlled and reproduction ofan audio signal having a broad band is made possible.

[0126] In the above-described embodiment, the high-efficiency codingsignal 801 having the dummy data embedded therein and the truequantization accuracy information and/or true normalization factorinformation (second code string or its partial code string) 806 forreplacing the dummy data are acquired from the server side via the samepublic network. However, for example, the high-efficiency coding signal801 having a large quantity of dummy data embedded therein may beacquired through a satellite network with a high transmission rate whilethe true quantization accuracy information and/or true normalizationfactor information 806 having a small quantity of data may be separatelyacquired by using a telephone line or a network with a relatively lowtransmission rate such as ISDN. The signal 801 may also be supplied on alarge-capacity recording medium such as CD-ROM or DVD (digital versatiledisk)-ROM. The above-described structure enables enhanced security.

[0127] Meanwhile, the tonal component and the non-tonal component aredescribed with reference to FIG. 13. The rewriting of the dummy data inthe high-efficiency coding signal having the dummy data embedded thereinmay be performed with respect to quantization accuracy informationand/or normalization factor information constituting tonal components,quantization accuracy information and/or normalization factorinformation constituting non-tonal components, or quantization accuracyinformation and/or normalization factor information constituting bothtonal components and non-tonal components.

[0128]FIG. 18 shows a specific example of the format of the trueinformation (second code string) of the signal 807 from the controlmeans 1805 of FIG. 17. This format is for changing the information ofthe N-th frame shown in FIG. 14 to the information shown in FIG. 9.Thus, with a code string in which there still is dummy data, areproduced sound having the spectrum shown in FIG. 15 is changed to areproduced sound having the spectrum shown in FIG. 8.

[0129]FIG. 19 is a block diagram showing an example of recording meansused in the embodiment of the present invention. In FIG. 19, an inputsignal 821 is a first code string a part of which is replaced by dummydata. In this case, quantization accuracy information and normalizationfactor information on the high-frequency side constitute the dummy data.First, the content of the code string of the input signal 821 isresolved by code string resolution means 1821 and sent as a signal 822to code string rewriting means 1822. The code string rewriting means1822 receives true quantization accuracy information and normalizationfactor information 825, which is a second code string, as a signal 826through control means 1824. The code string rewriting means 1822rewrites the dummy part of the quantization accuracy information and thenormalization factor information of the signal 822 by using the signal826 and sends a signal 823 as a result of rewriting to recording means1823, where the signal is recorded to a recording medium. The recordingmedium for recording the code string of a signal 824 may be a recordingmedium on which the code string of the signal 821 was originallyrecorded.

[0130] In the embodiment shown in FIG. 19, similarly to theabove-described example shown in FIG. 17, at least a part of the dummydata may be rewritten by using a partial code string of the second codestring and then recorded, instead of rewriting (complementing) all thedummy data by using the second code string. In the case of thusreplacing at least a part of the dummy data by using the partial codestring of the second code string and then recording the data, forexample, the quality (sound quality or image quality) of the trialviewing/listening can be arbitrarily changed by arbitrarily changing theproportion of the partial code string of the second code string. In thiscase, even in the trial viewing/listening mode, the partial code stringof the second code string is inputted as the signal 825 to the controlmeans 1824 and then sent as the signal 826 to the code string rewritingmeans 1822. Therefore, a part of the dummy data embedded in the firstcode string from the code string resolution means 1821 may be rewrittenby using the partial code string of the second code string and then sentto the recording means 1823.

[0131] The reproducing device and the recording device used in theembodiment of the present invention are described above. It is alsopossible to encrypt the spectral coefficient information on thehigh-frequency side to further improve the security. In that case, thecode string rewriting means 1802, 1822 for replacing the dummy data,shown in FIGS. 17 and 19, receive the true normalization factorinformation through the control means 1805, 1824 to replace the dummydata. The code string rewriting means 1802, 1822 also decode the data onthe high-frequency side by using a decryption key acquired through thecontrol means 1805, 1824 and reproduce or record the data.

[0132]FIG. 20 shows a specific example of the format of information forreplacing dummy data in the case where a tonal component is separated asshown in FIG. 10 and coded as shown in FIG. 13. Thus, a reproduced soundhaving the spectrum shown in FIG. 15 is substantially changed to areproduced sound having the spectrum shown in FIG. 10.

[0133]FIG. 21 is an exemplary flowchart showing the procedure in thecase of reproduction using software in accordance with the reproducingmethod used in the embodiment of the present invention. First, at stepS11, a code string (first code string) containing dummy data isresolved, and then at step S12, whether to carry out reproduction withhigh sound quality is determined. If reproduction with high soundquality is to be carried out, at step S13, the dummy data in the firstcode string is replaced by true data (second code string) for providinga broad band, and then the procedure goes to step S14. Otherwise, theprocedure goes directly to step S14. The signal components are decodedat step S14 and inverse transform to a time series signal to reproduceits sound at step S15.

[0134]FIG. 22 is an exemplary flowchart showing the procedure in thecase of recording using software in accordance with the recording methodused in the embodiment of the present invention. First, at step S21,whether to carry out recording with high sound quality is determined. Ifrecording with high sound quality is to be carried out, first, at stepS22, a code string (first code string) containing dummy data isresolved, and then at step S23, the dummy data in the code string isreplaced by true data (second code string) for providing a broad band.The procedure then goes to step S24. Otherwise, the procedure goesdirectly to step S24 from step S21.

[0135] Meanwhile, in the above-described embodiment, a part of data of acode string is replaced by dummy data such as 0 without changing thestructure of the code string of a predetermined format obtained bycoding a signal, that is, in conformity with the existing code stringformat standard. However, it is also possible to remove the dummy datapart and thus shorten the code string.

[0136] Specifically, FIG. 23 shows a code string such that dummyquantization accuracy data (0) of the quantization accuracy informationQN the dummy normalization factor data (0) of the normalization factorinformation NP in the code string shown in FIG. 14 are deleted and theremaining part is moved over to shorten the code string. In this case,information of the number of units of the dummy data must be written inthe code string. For example, the number of dummy coding units may bewritten instead of the number of coding units UN, or the number of dummycoding units may be written in a reserved area or the like.

[0137] If the dummy data is left as in the example shown in FIG. 14,when later complementing the code string data by using the second codestring, the dummy data part is overwritten by the second code string. Onthe other hand, in the example shown in FIG. 23, processing to insertthe second code string into the part where the dummy data was deleted isnecessary. However, the example of FIG. 23 is advantageous in that asmaller quantity of data may be transmitted or recorded because thelength of the code string is shorter by the length of the dummy data ofFIG. 14.

[0138] As is apparent from the above description, in the coding methodused in the embodiment of the present invention, a signal having anarrow reproducing band is reproduced as dummy data such asnormalization factor data or the like is written for each frame.However, it is also possible to change the reproducing band using thisdummy data such as normalization factor data, depending on each part ofa tune.

[0139] If trial viewing/listening is of low quality (sound quality orimage quality), the quality of a signal that can be enjoyed after thepurchase is unknown and it is difficult to determine whether to purchaseor not. However, if trial viewing/listening of relatively high qualityis possible, the quality of the reproduced signal of the first codestring is changed with the lapse of time so that only a part of thereproduced signal may be reproduced with high quality, considering thatmore users may think they can sufficiently enjoy the signal withoutpurchasing.

[0140] Specifically, for example, in the frames of the leading part of atune and the most impressive part of the tune, coding is performedwithout using dummy data such as normalization factor data so as toenable reproduction of a broad band, whereas in the frames of the otherparts, dummy data such as normalization factor data is used to performnarrow-band reproduction. By smoothly changing the reproducing band overseveral frames, it is possible to reduce the unnaturalness in the triallistening (in general, trial viewing/listening).

[0141]FIG. 24 shows a change of the reproducing band in this triallistening based on this method. The reproducing band is broadened in theleading part Ka and the most impressive part Kb of a tune, and forexample, the intermediate/high-frequency band cannot be reproduced inthe other parts because of the dummy data.

[0142] To generalize this, when generating a first code string of atrial viewing/listening code string, the value of a control parameterfor the quality (sound quality or image quality) of the reproducedsignal of the first code string for trial viewing/listening is changedwith the lapse of time. This reproduction quality control is carried outby embedding dummy data into the code string and the bandwidth of thecoded signal may be used as a reproduction quality control parameter. Inthe case where, when reproducing a code string of a predetermined formatobtained by coding a signal, at least a part of dummy data of a firstcode string made through replacing at least a part of the code string ofthe predetermined format with the dummy data is rewritten by using apartial code string of a second code string for complementing the dummydata part, and the code string obtained by the rewriting with thepartial code string of the second code string is decoded, spectraltransform of the input signal and division of its band are performed inthe coding, thus generating the code string of the predetermined formatcomprising quantization accuracy information, normalization factorinformation and spectral factor information for each band. The dummydata corresponds to the information of at least the high-frequency sideof at least one of the quantization accuracy information, thenormalization factor information and the spectral coefficientinformation. The partial code string of the second code string is theinformation of at least the low-frequency side of the informationcorresponding to the dummy data, and its band changes with the lapse oftime.

[0143]FIG. 25 is a block diagram showing a specific example of a codingdevice for changing the quality of a reproduced signal depending on eachpart of the tune. In FIG. 25, control means 1844 receives information845 of the leading part and the most impressive part of the tune andcontrols signal component coding means 1842 to use dummy data such asnormalization factor data, thus changing the reproducing band.

[0144] The other parts of FIG. 25 are similar to those of FIG. 2. Thatis, after an inputted waveform signal 841 is transformed to signals 842of signal frequency components by transform means 1841, each componentis coded by the signal component coding means 1842 and a code string 844is generated by code string generation means 1843.

[0145]FIG. 26 is a flowchart showing the flow of a specific example ofthe processing by the control means 1844 FIG. 25 to change thereproducing band. First, the frame number N is set to 1 at step S31 andthen the processing goes to step S32. At step S32, it is determinedwhether or not the current frame is a broad-band reproducing sectionsuch as the leading part or the most impressive part. If the currentframe is a broadband reproducing section, at step S33, coding is carriedout without using dummy data such as normalization factor data so as tocarry out broad-band reproduction, and the processing goes to step S37.Otherwise, the processing goes to step S34. At step S34, it isdetermined whether or not the current frame is a band interpolationsection before or after a broad-band reproducing section. If the currentframe is a band interpolation section, at step S35, coding is carriedout using dummy data such as normalization factor data so that thereproducing band gradually changes, and the processing goes to step S37.Otherwise, the processing goes to step S36. At step S36, coding iscarried out using dummy data such as normalization factor data so as toperform narrow-band reproduction, and the processing goes to step S37.At step S37, it is determined whether the current frame is the lastframe or not. If the current frame is the last frame, the processingends. Otherwise, at step S38, the value of the frame number N isincreased by 1 to shift to the next frame, and the processing goes backto step S32.

[0146] In this example, dummy data such as normalization factor data isused for controlling the reproducing band in each frame. However,encryption of the high-frequency side may also be used for controllingthe reproducing band, as described in the Japanese Publication ofUnexamined Patent Application No.H10-135944 proposed by the presentinventors.

[0147]FIG. 27 shows a method for encrypting the high-frequency side ofeach frame by using a technique similar to the technique described inthe Japanese Publication of Unexamined Patent Application No.H10-135944.In the specific example shown in FIG. 27, spectral coefficientinformation SP_(H) on the high-frequency side, normalization factorinformation NP_(H) on the high-frequency side, quantization accuracyinformation QN_(H) on the high-frequency side, and the number of codingunits UN thereof are encrypted.

[0148] By thus limiting the band and changing the bandwidth availablefor trial listening with the lapse of time as shown in FIG. 24, anothermethod of the embodiment of the present invention is made possible.Thus, again, it is possible to enjoy a tune with high sound quality bycarrying out decryption after confirming the sound quality and thecontent of the tune.

[0149] Meanwhile, in the case where broad-band reproduction is madepossible in the frames of, for example, the leading part of the tune andthe most impressive part of the tune so that the quality of thereproduced signal changes with the lapse of time, as described abovewith reference to FIG. 24, it is preferred that the time of trialviewing/listening can be shortened by extracting and reproducing onlythe leading part and the most impressive part and that the user canselect such a short-time trial viewing/listening mode or a trialviewing/listening mode for the entire content.

[0150] That is, when a code string such that the quality of thereproduced signal changes with the lapse of time is used as the firstcode string having the dummy data embedded therein, a part on the timeaxis of the reproduced signal of the first code string with its qualitybeing within a predetermined range may be extracted and reproduced.

[0151] A specific example is shown in FIGS. 28A and 28B. In FIG. 28A,similar to FIG. 24, the reproducing band is broadened with the lapse oftime in a part of a tune, for example, th leading part Ka of the tuneand the most impressive part Kb of the tune, and for example, theintermediate/high-frequency band cannot be reproduced in the other partsbecause of the dummy data. With respect to such a tune having areproducing band changing with the lapse of time, the content of thetune can be confirmed in a short trial listening time by extracting andreproducing the parts having the broad band, that is, the leading partKa and the most impressive part Kb of the tune, as shown in FIG. 28B.

[0152] The trial viewing/listening in the embodiment of the presentinvention and the exemplary method for improving its quality aredescribed above. Hereinafter, a content supply system using theembodiment of the present invention will be described.

[0153]FIG. 29 is a view for explaining the content supply system usingthe embodiment of the present invention. In FIG. 29, a center (contentsupply center) 1865 for storing and managing contents and user terminals1861 to 1864 used by respective users are connected by networks (861 to868). The user terminals 1861 to 1864 are directly connected to thecenter 1865.

[0154]FIG. 30 is a block diagram showing a specific example of the userterminal. The user terminal has communication means 1881 for performingcommunication using a signal 881 to and from the center and the otheruser terminals, and control means 1882 for controlling suchcommunication. The user terminal also has recording means 1884 capableof recording trial listening data using dummy data sent from the center,and reproducing means 1885. Thus, each user can listen to the triallistening data sent from the center, many times. For example, the usermay reproduce trial listening data sequentially sent from the centerduring the night, with relatively low sound quality as background musicduring the day.

[0155] Meanwhile, the user terminal has signal synthesis means 1886 andwriting means 1887. Thus, the user can synthesize trial listening datacontaining dummy data and high-sound-quality data made up of not dummydata but true normalization factor information and the like, and canreproduce the high-quality audio signal using the reproducing means 1885or record the high-quality audio signal to a recording medium 1888 viathe writing means 1887. The high-sound-quality data is purchased by theuser via the control means 1882 if the user likes a specific tune. Thehigh-sound-quality data is sent in an encrypted state from the center,temporarily recorded to the recording means 1884, and then sent todecryption means 1883.

[0156] The decryption means 1883 decrypts encrypted high-sound-qualitydata 886 by using a decryption key 892 sent from the control means 1882and sends the decrypted data to the signal synthesis means 1886. In viewof the protection of data, it is desired that the decryption means 1883,the signal synthesis means 1886, the writing means 1887 and thereproducing means 1885 are integrated in terms of hardware.

[0157]FIG. 31 is a block diagram showing a specific example of thecontrol means of FIG. 30. This control means has right informationstorage means 1904 as well as a CPU 1902, a memory 1903 and input/outputmeans 1901. Token information is stored in the right information storagemeans 1904. This token information is purchased by a user paying its feein advance. The token information is reduced every time a tune ispurchased. Such right information storage means 1904 can be realized byusing, for example, an IC card. The method for improving the soundquality of each tune, that is, the method for settlement of the purchaseof the tune, may be a method other than such a prepaid method, forexample, a credit card method.

[0158] In the specific example of FIG. 29, the trial listening datacontaining dummy data is distributed by using the same network as thehigh-sound-quality data. However, this is not necessarily required anddistribution via broadcast or CD-ROM which enables easy transmission ofa large quantity of data may be used.

[0159] In the case where the distribution of trial listening data fromthe center to the user terminal is separately carried out by using anetwork or the like, a database is provided at the center and triallistening data of tunes of a genre from which the user purchasedhigh-sound-quality data may be sent to the user intensively.

[0160] In this manner, in the content supply system using the embodimentof the present invention, content data for trial viewing/listening issent for free or at a low price from the center to the user terminal.The user terminal reproduces the contents for trial viewing/listeningand the user selects and purchases only the content that the user likes,thus enabling reproduction with high quality. The reception of thecontents for trial viewing/listening may be carried out on the basis ofmembership for free or at a low price.

[0161]FIG. 32 is a view for explaining another example of the contentsupply system using the embodiment of the present invention. In FIG. 32,a center (content supply center) 1865 and the user terminals 1861 to1864 are the same as those of FIG. 29. First, the user terminal 1861receives, from the center, trial listening data 921 containing dummydata and reproduced with relatively low sound quality. If the user ofthe user terminal 1861 likes this tune, the user purchaseshigh-sound-quality data 925 obtained by replacing the dummy data withtrue data. The user sends a copy 922 of the data 921 to the userterminal 1862, considering that also the user of the user 1862 likesthis tune. In this case, the user of the user terminal 1862 can receivethis trial listening data 922 for free or at a low price and reproducethe trial listening data 922. If the user of the user terminal 1862likes this tune, the user purchases high-sound-quality data 926 of thesame content as the data 925 from the center 1865.

[0162] Similarly to the user of the user terminal 1861, the user of theuser terminal 1862 sends a copy 923 of the data 922 to the user terminal1863, considering that also the user of the user 1863 likes this tune.In this case, too, the user of the user terminal 1863 can receive thiscopy for free or at a low price. If the user of the user terminal 1863likes this tune, the user can purchase high-sound-quality data 927 ofthe same content as the data 925 from the center 1865. The user of theuser terminal 1863 can also send a copy 924 of the data 923 to the userterminal 1864.

[0163] In this another example of the content supply system using theembodiment of the present invention, similar copying of the triallistening data for free or at a low price among the users is permittedand only the user who listens to and likes the tune will purchase thehigh-sound-quality data and listen to the tune with high sound quality.In this case, the user purchases the high-sound-quality data withrespect to the trial listening data having dummy data. However, a keyfor decrypting encrypted high-frequency data may be purchased, as in thetechnique described in the Japanese Publication of Unexamined PatentApplication No.H10-135944.

[0164]FIG. 33 is a view for explaining still another example of thecontent supply system using the embodiment of the present invention. Inthis system, first, trial listening data 941 with its band narrowed, forexample, by using dummy data, is written to a recording medium 1942 forfree or at a low price from a content supply terminal 1941 such as an avending machine installed at a convenience store or a so-called kiosk,and the recording medium 1942 is loaded on a reproducing terminal 1943to reproduce the data. The reception of the content for trial listeningviewing/listening may be carried out on the basis of membership for freeor at a low price.

[0165]FIG. 34 is a block diagram showing a specific example of thereproducing terminal of FIG. 33. A recording medium 1968 is the same asthe recording medium 1942 of FIG. 33. This reproducing terminal also hasa recording function, as will be described later. The content of triallistening data recorded on the recording medium may be reproduced asmuch as the user likes, by using reading means 1966 and reproducingmeans 1967. If the user likes this tune, the user purchaseshigh-sound-quality data 963 through communication means 1961 under thecontrol of control means 1962. This high-sound-quality data 963 has beenencrypted similarly to the example of FIG. 30. The high-sound-qualitydata 963 is decrypted by decryption means 1963 and then synthesized bysignal synthesis means 1964 with trial listening data containing dummydata temporarily read out from the recording medium by the reading means1966. High-sound-quality data 967 thus obtained is written to therecording medium 1968 by writing means 1965.

[0166] In view of the protection of data, it is desired that thedecryption means 1963, the signal synthesis means 1964 and the writingmeans 1965 are integrated in terms of hardware.

[0167] As a method for settlement at the time of purchase, the samemethod as in the case of FIG. 30 may be applied. In this example, theuser purchases the high-sound-quality data with respect to the triallistening data having dummy data. However, a key for decryptingencrypted high-frequency data may be purchased, as in the techniquedescribed in the Japanese Publication of Unexamined Patent ApplicationNo.H10-135944. That is, in the content supply system described withreference to FIGS. 33 and 34, content data for trial viewing/listeningdownloaded for free or at a low price from a kiosk terminal or the likeis recorded to a recording medium. The user reproduces the contents,selects only the content that the user likes, and purchases itshigh-sound-quality data, thus enabling reproduction with high quality.

[0168] If the reproducing terminal of FIG. 33 is to perform only trialviewing/listening, the reproducing terminal need not have thecommunication means 1961, the decryption means 1963, the signalsynthesis means 1964, the writing means 1965 and the like as in thereproducing terminal of FIG. 34. The sound quality may be improved by aterminal as shown in FIG. 34 after trial listening is sufficient carriedout by ordinary reproducing means for the recording medium 1942.

[0169] While audio signals are used in the above-described embodiment,the present invention can also be applied to image signals.Specifically, for example, in the case where an image signal istransformed for each block by using two-dimensional DCT and quantized byusing various quantization tables, a dummy quantization table havinghigh-frequency components eliminated therefrom is designated, and thedummy quantization table is replaced by a true quantization table havinghigh-frequency components therein when improving the image quality.Thus, it is possible to perform processing similar to the case of audiosignals.

[0170] The present invention can also be applied to a system in which anentire code string is encrypted and the encrypted code string isdecrypted during reproduction.

[0171] While a coded bit stream is recorded to a recording medium in theabove-described embodiment, the method of the present invention may alsobe applied to the case of transmitting a bit stream. Thus, for example,only a listener who acquired a true normalization factor over the entireband may be allowed to reproduce a broadcast audio signal with highsound quality, while the other listeners can sufficiently grasp thecontent but can only reproduce the audio signal with relatively lowsound quality.

1. (Amended) A signal processing system for a code string of apredetermined format obtained by coding a signal, the system comprising:first code string generation means for generating a first code string byreplacing a part of the code string of the predetermined format withdummy data; second code string generation means for generating a secondcode string for complementing the dummy data part of the first codestring; first code string provision means for providing the first codestring; second code string provision means for providing the second codestring; rewriting means for rewriting the dummy data of the first codestring received from the first code string provision means to the secondcode string received from the second code string provision means; andswitching means for switching and outputting the first code string andthe code string from the rewriting means in accordance with apredetermined condition; wherein the code string of the predeterminedformat comprises normalization factor information of the signal; and thedummy data comprises dummy data corresponding to at least a part of thenormalization factor information.
 2. (Amended) A signal processingsystem for a code string of a predetermined format obtained by coding asignal, the system comprising: first code string generation means forgenerating a first code string by replacing a part of the code string ofthe predetermined format with dummy data; second code string generationmeans for generating a second code string for complementing the dummydata part of the first code string; first code string provision meansfor providing the first code string; second code string provision meansfor providing the second code string; rewriting means for rewriting thedummy data of the first code string received from the first code stringprovision means to the second code string received from the second codestring provision means; and switching means for switching and outputtingthe first code string and the code string from the rewriting means inaccordance with a predetermined condition; wherein the code string ofthe predetermined format comprises a variable-length code string atleast partly; and the dummy data comprises dummy data corresponding toat least a part of the variable-length code string.
 3. (Amended) Asignal processing device for a code string of a predetermined formatobtained by coding a signal, the device comprising: first code stringgeneration means for generating a first code string by replacing a partof the code string of the predetermined format with dummy data; andsecond code string generation means for extracting the part of the codestring of the predetermined format replaced by the dummy data at thefirst code string generation means, and generating from the part asecond code string for complementing the dummy data part of the firstcode string; wherein the code string of the predetermined format can begenerated by rewriting the dummy data of the first code string to thesecond code string and then switching and outputting the first codestring and the code string after the rewriting in accordance with apredetermined condition; the code string of the predetermined formatcomprises normalization factor information of the signal; and the dummydata comprises dummy data corresponding to at least a part of thenormalization factor information.
 4. (Amended) A signal processingdevice for a code string of a predetermined format obtained by coding asignal, the device comprising: first code string generation means forgenerating a first code string by replacing a part of the code string ofthe predetermined format with dummy data; and second code stringgeneration means for extracting the part of the code string of thepredetermined format replaced by the dummy data at the first code stringgeneration means, and generating from the part a second code string forcomplementing the dummy data part of the first code string; wherein thecode string of the predetermined format can be generated by rewritingthe dummy data of the first code string to the second code string andthen switching and outputting the first code string and the code stringafter the rewriting in accordance with a predetermined condition; thecode string of the predetermined format comprises a variable-length codestring at least partly; and the dummy data comprises dummy datacorresponding to at least a part of the variable-length code string. 5.(Amended) The signal processing device as claimed in claim 4, whereinthe second code string comprises at least a part of the code string ofthe predetermined format as dummy data.
 6. (Amended) The signalprocessing device as claimed in claim 4, wherein in the coding, a codestring of the predetermined format comprising spectral coefficientinformation for each band of an input signal is generated, in the codestring of the predetermined format, at least the spectral coefficientinformation is coded to a variable-length code string, and the dummydata comprises dummy data corresponding to a part of the spectralcoefficient information.
 7. (Amended) The signal processing device asclaimed in claim 4, wherein a part of the spectral coefficientinformation is information of a mid frequency band of the spectralcoefficient information.
 8. (Amended) The signal processing device asclaimed in claim 4, wherein in the coding, a code string of thepredetermined format comprising quantization accuracy information foreach band of an input signal is generated, and the dummy data furthercomprises dummy data of at least a part of the quantization accuracyinformation.
 9. (Amended) The signal processing device as claimed inclaim 4, wherein in the coding, a code string of the predeterminedformat comprising normalization factor information for each band of aninput signal is generated, and the dummy data further comprises dummydata of at least a part of the normalization factor information. 10.(Amended) A signal processing method for a code string of apredetermined format obtained by coding a signal, the method comprising:a first code string generation step of generating a first code string byreplacing a part of the code string of the predetermined format withdummy data; and a second code string generation step of extracting thepart of the code string of the predetermined format replaced by thedummy data at the first code string generation step, and generating fromthe part a second code string for complementing the dummy data part ofthe first code string; wherein the code string of the predeterminedformat can be generated by rewriting the dummy data of the first codestring to the second code string and then switching and outputting thefirst code string and the code string after the rewriting in accordancewith a predetermined condition; the code string of the predeterminedformat comprises normalization factor information of the signal; and thedummy data comprises dummy data corresponding to at least a part of thenormalization factor information.
 11. (Amended) A signal processingmethod for a code string of a predetermined format obtained by coding asignal, the method comprising: a first code string generation step ofgenerating a first code string by replacing a part of the code string ofthe predetermined format with dummy data; and a second code stringgeneration step of extracting the part of the code string of thepredetermined format replaced by the dummy data at the first code stringgeneration step, and generating from the part a second code string forcomplementing the dummy data part of the first code string; wherein thecode string of the predetermined format can be generated by rewritingthe dummy data of the first code string to the second code string andthen switching and outputting the first code string and the code stringafter the rewriting in accordance with a predetermined condition; thecode string of the predetermined format comprises a variable-length codestring at least partly; and the dummy data comprises dummy datacorresponding to at least a part of the variable-length code string. 12.(Amended) The signal processing method as claimed in claim 11, whereinthe second code string comprises at least a part of the code string ofthe predetermined format as dummy data.
 13. (Amended) The signalprocessing method as claimed in claim 11, wherein in the coding, a codestring of the predetermined format comprising spectral coefficientinformation for each band of an input signal is generated, in the codestring of the predetermined format, at least the spectral coefficientinformation is coded to a variable-length code string, and the dummydata comprises dummy data corresponding to a part of the spectralcoefficient information.
 14. (Amended) The signal processing method asclaimed in claim 11, wherein a part of the spectral coefficientinformation is information of a mid frequency band of the spectralcoefficient information.
 15. (Amended) The signal processing method asclaimed in claim 11, wherein in the coding, a code string of thepredetermined format comprising quantization accuracy information foreach band of an input signal is generated, and the dummy data furthercomprises dummy data of at least a part of the quantization accuracyinformation.
 16. (Amended) The signal processing method as claimed inclaim 11, wherein in the coding, a code string of the predeterminedformat comprising normalization factor information for each band of aninput signal is generated, and the dummy data further comprises dummydata of at least a part of the normalization factor information. 17.(Amended) A signal processing device for a code string of apredetermined format obtained by coding a signal, the device comprising:provision means for providing a first code string in which a part of thecode string of the predetermined format is replaced by dummy data;wherein the code string of the predetermined format can be generated byrewriting the dummy data of the first code string to a second codestring for complementing the dummy data part and then switching andoutputting the first code string and the code string after the rewritingin accordance with a predetermined condition; the code string of thepredetermined format comprises normalization factor information of thesignal; and the dummy data comprises dummy data corresponding to atleast a part of the normalization factor information.
 18. (Amended) Asignal processing device for a code string of a predetermined formatobtained by coding a signal, the device comprising: provision means forproviding a first code string in which a part of the code string of thepredetermined format is replaced by dummy data; wherein the code stringof the predetermined format can be generated by rewriting the dummy dataof the first code string to a second code string for complementing thedummy data part and then switching and outputting the first code stringand the code string after the rewriting in accordance with apredetermined condition; the code string of the predetermined formatcomprises a variable-length code string at least partly; and the dummydata comprises dummy data corresponding to at least a part of thevariable-length code string.
 19. (Amended) A signal processing methodfor a code string of a predetermined format obtained by coding a signal,the method comprising: a provision step of providing a first code stringin which a part of the code string of the predetermined format isreplaced by dummy data; wherein the code string of the predeterminedformat can be generated by rewriting the dummy data of the first codestring to a second code string for complementing the dummy data part andthen switching and outputting the first code string and the code stringafter the rewriting in accordance with a predetermined condition; thecode string of the predetermined format comprises normalization factorinformation of the signal; and the dummy data comprises dummy datacorresponding to at least a part of the normalization factorinformation.
 20. (Amended) A signal processing method for a code stringof a predetermined format obtained by coding a signal, the methodcomprising: a provision step of providing a first code string in which apart of the code string of the predetermined format is replaced by dummydata; wherein the code string of the predetermined format can begenerated by rewriting the dummy data of the first code string to asecond code string for complementing the dummy data part and thenswitching and outputting the first code string and the code string afterthe rewriting in accordance with a predetermined condition; the codestring of the predetermined format comprises a variable-length codestring at least partly; and the dummy data comprises dummy datacorresponding to at least a part of the variable-length code string. 21.(Amended) A signal processing device for a code string of apredetermined format obtained by coding a signal, the device comprising:provision means for providing a second code string for complementing adummy data part of a first code string in which a part of the codestring of the predetermined format is replaced by dummy data; whereinthe code string of the predetermined format can be generated byrewriting the dummy data of the first code string to the second codestring and then switching and outputting the first code string and thecode string after the rewriting in accordance with a predeterminedcondition; the code string of the predetermined format comprisesnormalization factor information of the signal; and the dummy datacomprises dummy data corresponding to at least a part of thenormalization factor information.
 22. (Amended) A signal processingdevice for a code string of a predetermined format obtained by coding asignal, the device comprising: provision means for providing a secondcode string for complementing a dummy data part of a first code stringin which a part of the code string of the predetermined format isreplaced by dummy data; wherein the code string of the predeterminedformat can be generated by rewriting the dummy data of the first codestring to the second code string and then switching and outputting thefirst code string and the code string after the rewriting in accordancewith a predetermined condition; the code string of the predeterminedformat comprises a variable-length code string at least partly; and thedummy data comprises dummy data corresponding to at least a part of thevariable-length code string.
 23. (Amended) A signal processing methodfor a code string of a predetermined format obtained by coding a signal,the method comprising: a provision step of providing a second codestring for complementing a dummy data part of a first code string inwhich a part of the code string of the predetermined format is replacedby dummy data; wherein the code string of the predetermined format canbe generated by rewriting the dummy data of the first code string to thesecond code string and then switching and outputting the first codestring and the code string after the rewriting in accordance with apredetermined condition; the code string of the predetermined formatcomprises normalization factor information of the signal; and the dummydata comprises dummy data corresponding to at least a part of thenormalization factor information.
 24. (Amended) A signal processingmethod for a code string of a predetermined format obtained by coding asignal, the method comprising: a provision step of providing a secondcode string for complementing a dummy data part of a first code stringin which a part of the code string of the predetermined format isreplaced by dummy data; wherein the code string of the predeterminedformat can be generated by rewriting the dummy data of the first codestring to the second code string and then switching and outputting thefirst code string and the code string after the rewriting in accordancewith a predetermined condition; the code string of the predeterminedformat comprises a variable-length code string at least partly; and thedummy data comprises dummy data corresponding to at least a part of thevariable-length code string.